molecules:ism:ch3c4h [CDMS classic documentation]

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===== Reports on the Detection of 1,3-Pentadiyne in the ISM =====

The 1,3-pentadiyne molecule CH<sub>3</sub>C<sub>4</sub>H, aka methyldiacetylene, had been identified in spectra recorded toward TMC-1 by two groups independently and at almost the same time\\
J. M. MacLeod, L. W. Avery, N. W. Broten,\\
**[[https://ui.adsabs.harvard.edu/abs/1984ApJ...282L..89M|The detection of interstellar methyldiacetylene (CH<sub>3</sub>C<sub>4</sub>H)]]**\\
//Astrophys. J.// **282**, L89–L92 (1984);\\
C. M. Walmsley, P. R. Jewell, L. E. Snyder, and G. Winnewisser,\\
**[[https://ui.adsabs.harvard.edu/abs/1984A%26A...134L..11W|Detection of interstellar methyldiacetylene (CH<sub>3</sub>C<sub>4</sub>H) in the dark dust cloud TMC 1]]**\\
//Astron. Astrophys.// **184**, L11–L14 (1984).\\
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The molecule was also detected by\\
M. Araki, S. Takano, N. Sakai, S. Yamamoto, T. Oyama, N. Kuze, and K. Tsukiyama,\\
who studied\\
**[[https://doi.org/10.3847/1538-4357/aa8637|Long Carbon Chains in the Warm Carbon-chain-chemistry Source L1527: First Detection of C<sub>7</sub>H in Molecular Clouds]]**,\\
//Astrophys. J.// **847** Art. No. 51 (2017).\\
The three //J// = 11 – 10 transitions with //K// = 0, 1, and 2 were detected near 44.8 GHz with the 100 m GBT.\\
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C. Cabezas, R. Fuentetaja, E. Roueff, M. Agúndez, B. Tercero, N. Marcelino, J. R. Pardo, P. de Vicente and J. Cernicharo\\
reported on\\
**[[https://doi.org/10.1051/0004-6361/202142814|New Deuterated Species in TMC-1: Detection of CH<sub>2</sub>DC<sub>4</sub>H with the QUIJOTE line survey]]**,\\
//Astron. Astrophys.// **657** Art. No. L5 (2022).\\
Twelve transition with //J// = 8 to 12 and //K<sub>a</sub>// ≤ 1 were detected with the Yebes 40 m radio telescope. The CH<sub>3</sub>C<sub>4</sub>H to CH<sub>2</sub>DC<sub>4</sub>H abundance ratio of 24 ± 2 is very similar to that of CH<sub>3</sub>C<sub>3</sub>N to CH<sub>2</sub>DC<sub>3</sub>N ratio of 22 ± 2.\\
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More recently,\\
C. Cabezas, M. Agúndez, E. Roueff, R. Fuentetaja, B. Tercero, N. Marcelino, P. de Vicente, and J. Cernicharo\\
announced the\\
**[[https://doi.org/10.1051/202557754|Detection of Six Isotopologues of CH<sub>3</sub>CCCCH in TMC-1 with the QUIJOTE Line Survey]]**,\\
//Astron. Astrophys.// **703** Art. No. L22 (2025).\\
With an increase of the signal-to-noise ratio in comparison to the previous item, the authors were able to identify transition with //J// = 8 to 12 and //K<sub>a</sub>// ≤ 1 of all five singly substituted <sup>13</sup>C isotopologs and of CH<sub>3</sub>C<sub>4</sub>D with reasonable to good S/N and mostly not or only slightly blended. The lowest //J// pair of CH<sub>3</sub>C<sub>4</sub>D transitions was not covered. The <sup>12</sup>C/<sup>13</sup>C ratio is 93 ± 11, while the H/D ratio in the case of CH<sub>3</sub>C<sub>4</sub>D is 54 ± 8.\\
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Contributor(s): H. S. P. Müller; 7, 2004; 10, 2017; 03, 2022; 11, 2025

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